Your child is 3 now. Soon, he will 'graduate' to a bike without training wheels.
Don't know what the 'age' range is for a balance bike.
Also to consider, is the height, of your child and that kids grow pretty fast.
For our kids, they both had bikes, with training wheels. I had that too, as a kid. But REAL soon after, both my kids were just riding without training wheels. They learn balance just from a regular bike... which was sized to them, per their height.
At 4, my son could ride without training wheels. And was just riding a regular bike after we took off the training wheels.
Easy.